Variable habitat selection and space use among bullsnake (Pituophis catenifer sayi) populations: distance between seasonal habitats drives space use A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements For the Degree of Master of Science in Biology University of Regina By Tera Lynn Edkins Regina, Saskatchewan April, 2017 ©2017: T. L. Edkins UNIVERSITY OF REGINA FACULTY OF GRADUATE STUDIES AND RESEARCH SUPERVISORY AND EXAMINING COMMITTEE Tera Lynn Edkins, candidate for the degree of Master of Science in Biology, has presented a thesis titled, Variable habitat selection and space use among bullsnake (Pituophis catenifer sayi) populations: distance between seasonal habitats drives space use, in an oral examination held on April 24, 2017. The following committee members have found the thesis acceptable in form and content, and that the candidate demonstrated satisfactory knowledge of the subject material. External Examiner: *Dr. Donald McAlpine, New Brunswick Museum Co-Supervisor: Dr. Christopher Somers, Department of Biology Co-Supervisor: Dr. Raymond Poulin, Department of Biology, Adjunct Committee Member: Dr. Mark Brigham, Department of Biology Chair of Defense: Dr. Katya Herman, Faculty of Kinesiology and Health Studies *Via tele/videoconference Abstract The distribution of resources determines space use and habitat selection by snakes. Particularly in northern areas, the proximity of overwintering den sites to summering habitat likely influences space use. The resources driving seasonal movements among habitats may vary among populations and thus, space and habitat requirements may also vary. In addition, human modification may affect resource use by altering available habitats and resources. Although previous studies have reported differences in spatial ecology among populations, the driving factors of this variation remain to be addressed for many species. Bullsnakes (Pituophis catenifer sayi) reach their northern range limits in southern Saskatchewan, where they are currently listed as Data Deficient by the Committee on the Status of Endangered Wildlife in Canada. Many studies have focused on core range areas, while northern studies have focused on one population in the Frenchman River Valley, Saskatchewan. The habitat and space requirements identified in these previous studies, however, may not be relevant to all bullsnake populations. I examined bullsnake space and habitat use among independent populations in three river valleys (Frenchman River, South Saskatchewan River, and Big Muddy Valleys) in Saskatchewan, with varying habitat types (natural and anthropogenic) and availability. I tracked bullsnakes using radio-telemetry, estimated home range areas and movement patterns, and measured third and fourth order habitat selection. The objectives of my research were (1) to examine the extent to which habitat selection and space use may vary among populations and (2) to identify important habitat features in common among snakes from different populations. II Saskatchewan bullsnakes demonstrated variable space use and movement patterns among populations, exceeding space use requirements previously observed in southern areas. One population (Big Muddy Valley), on average, used 2.7 to 3 times less space, travelled 2.3 to 2.7 times shorter distances from overwintering sites, and had greater home range overlap than snakes from the other populations (Frenchman and South Saskatchewan River Valleys). This suggests that bullsnakes in the Big Muddy Valley had a closer spatial association between seasonal habitats. Bullsnakes appear to be flexible in terms of their third order habitat selection. Native habitats were used as expected across all valleys, but human-modified habitats were used at different frequencies across populations. These differences in habitat selection among populations are most likely due to differences in habitat availability among landscapes. Fourth habitat selection, however, was similar among populations, with bullsnakes selecting for sites typically within 1 m of a refuge site (including burrows, cement pads, and rock piles). It appears that bullsnakes occupy variable-sized home ranges and move variable distances. Bullsnakes also appear to be flexible in terms of how they meet resource requirements across their geographic range via habitat selection at a broad spatial scale. My study did find, however, that at a fine spatial scale refuge sites are an important habitat feature for bullsnakes. Conservation and management strategies are typically broad and are implemented as if populations of the same species have similar habitat requirements. However, my results indicate that this is not the case. As such, management plans may not be applicable to all populations. III Acknowledgements First I would like to thank my co-supervisors Dr. Chris Somers and Dr. Ray Poulin for their support. Thank you for putting your faith in a snake newbie and for allowing me to gain experience in the field of conservation biology. Thank you to my committee member Mark Brigham for his valuable input and support over the course of my thesis. Thank you to Dr. Mark Vanderwel for his statistical guidance. I am grateful to my wonderful field assistants Leagh Vermeylen, Ana Pecorari, and Allie Gallon for the long hours they put in tracking snakes. Thank you for being patient with me as we learned the ropes of radio-telemetry together. Thanks to Danae Frier for teaching me the field techniques I required to complete my project. Thank you to my lab mates at the University of Regina for your helpful advice and for being the friendliest and most supportive lab group a grad student could ask for. I thank the Saskatchewan Parks staff and Big Muddy Valley landowners for their support and cooperation during the field season. Thank you to Dr. Tracy Fisher and the North Albert Veterinary Clinic for completing our snake surgeries for summer 2015. I also thank Dr. Miranda Sidar and Dr. Dennilyn Parker, in addition to the veterinarians of the Western College of Veterinary Medicine, for donating their services for the snake surgeries in 2016. I would like to thank the Friends of the Royal Saskatchewan Museum for presenting me with the first ever RSM Graduate Student Scholarship. I would also like to thank The Faculty of Graduate Studies and Research for the financial support they provided. Finally, I would like to thank the Royal Saskatchewan Museum for funding this research project. IV Dedication I would like to dedicate this thesis to my mom, dad and sister. I cannot describe how much I appreciate everything you have done for me. Thank you for your constant encouragement and for always supporting my dreams, even if they were to be a crazy snake-studying scientist. I would also like to dedicate this thesis to my best friend and partner, Daniel Blerot. This thesis would not exist if you had not supported me when I decided to move to Saskatchewan to get my Master’s degree. You always believe in me. I am incredibly grateful for everything you have done for me and everything you have put up with throughout this process. I love you and am looking forward to spending my life with you. V Table of contents Abstract…………………………………………………………………………………...II Acknowledgements………………………………………………………………………IV Dedication………………………………………………………………………………...V Table of contents…………………………………………………………………………VI List of tables……………………………………………………………………………VIII List of figures……………………………………………………………………..........XIII Chapter 1: General Introduction……………………………………………………..........1 Habitat selection by animals………………………………………………………2 Animal space use………………………………………………………………….4 Habitat selection in human-modified areas…………………………………..........5 Habitat selection in reptiles………………………………………………………..6 Habitat selection by snakes…………………………………………………..........7 Snakes in Saskatchewan…………………………………………………………..8 References…………………………………………………………………..........11 Chapter 2: Variable habitat selection and space use among bullsnake (Pituophis catenifer sayi) populations: distance between seasonal habitats drives space use…........................24 Introduction………………………………………………………………………25 Materials and Methods…………………………………………………………...28 Results……………………………………………………………………………38 Discussion…………………………………………………………………..........51 Conclusions………………………………………………………………………61 References…………………………………………………………………..........63 Chapter 3: Synthesis……………………………………………………………………..73 VI Conservation and management implications…………………………………….74 Future research…………………………………………………………………...78 References…………………………………………………………………..........82 VII List of Tables Chapter 2: Table 1. Mean (±SD) telemetry data, maximum displacement, and home range overlap of bullsnakes from three different river valleys in southern Saskatchewan: the Big Muddy Valley (BMV), South Saskatchewan River Valley (SSRV), and the Frenchman River Valley (FRV). N = total number of snakes tracked..…………………………………….39 Table 2. Top generalized linear model, null model, and all models with ΔAIC <3 evaluating the best predictor of the maximum displacement from overwintering den sites by Saskatchewan bullsnakes. Fixed effects included river valley, distance to nearest man- made structure (m), snout to vent length (SVL, cm), and snake sex. The number of model parameters (K), Akaike’s Information Criterion value corrected for small sample size (AICc), difference in AICc from the top model (ΔAIC), and the Akaike weights are presented. Model averaging was performed, with presented values including the different model parameter